1. Field of the Invention
The present invention relates to an organic electroluminescent device and a method of manufacturing the same. More particularly, the present invention relates to an organic electroluminescent device with an extended life span, and a method of manufacturing the same.
2. Description of the Related Art
Organic electroluminescent devices (organic EL devices) are self emission displays that emit light by recombination of electrons and holes in a thin layer made of a fluorescent or phosphorescent organic compound when a current is applied to the thin layer. The organic EL devices have advantages such as lightweight, simple constitutional elements, easy fabrication process, superior image quality, and wide viewing angle. In addition, the organic EL devices have electrical properties suitable for portable electronic equipment such as complete creation of moving pictures, high color purity, low power consumption, and low driving voltage.
However, the organic EL devices easily deteriorate due to entry of moisture. Therefore, an encapsulation structure preventing the entry of moisture is required.
Conventionally, a metal can or a glass substrate processed into a cap with a groove is used for preventing the entry of moisture. According to this method, for moisture absorption, a desiccant of a powder type is mounted in the groove or a desiccant of a film type adheres to the groove by means of a double-sided tape. However, in the case of the former, a process is complicated and a material and process cost is high. In addition, the entire thickness increases, and a substrate intended for encapsulation is not transparent, which makes it difficult to carry out front emission. On the other hand, in the case of the latter, there is a limitation in preventing the entry of moisture, and the desiccant of a film type is easily broken in a fabrication process or in use, thereby lowering durability and reliability. Therefore, the adhesion of the desiccant using a double-sided tape is impractical in mass production.
As another example for prevention of the entry of moisture, there is a method of forming a multilayer by alternately stacking an organic thin film, and an inorganic thin film made of SiO2 or Al2O3 between a cathode and an anode. However, such a stacking method increases a process cost, which is unfavorable to mass production.